Assessment of quality of life, pain level and disability outcomes after lumbar discectomy

This study aimed to assess the quality of life of 113 Caucasian patients with intervertebral disc (IVD) degeneration of the lumbosacral (L/S) spine who qualified for microdiscectomy during a 12-month period after surgery. Based on magnetic resonance imaging before the surgery, the degree of radiological advancement of the degenerative changes was determined according to the Pfirrmann grading scale from 1 to 5. To assess pain intensity, the Visual Analog Scale (VAS) was used; the Satisfaction with Life Scale (SWLS) was used to evaluate quality of life; and to assess the degree of ability, the Oswestry Low Back Pain Disability Questionnaire (ODI) was employed. The level of pain, assessed using the VAS, significantly changed in the months following the surgery, with the highest values noted before surgery and the lowest a year after. In turn, the results of the SWLS questionnaire revealed a significant increase in satisfaction with life in the subsequent stages of the study. The conducted correlation analysis revealed significant dependencies in terms of quality of life in regard to pain as well as degree of disability. The level of pain and degree of disability were closely related to the degree of radiological advancement of degenerative changes according to the Pfirrmann grading scale.


Results
In all patients, pain continued for at least 1 year; moreover, it was observed that the occurrence of advanced degenerative changes was significantly related to the period of time that pain persisted, more frequent receiving of NSAIDs and the ability to work and partake in sports ( Table 1). The significantly highest body mass was noted among patients with degree 5 advancement of changes (p < 0.05).
Significant diversity was not determined for the advancement of changes under the influence of smoking cigarettes, drinking alcohol, or education in the groups (p > 0.05).

Relationship between VAS, ODI and SWLS scores.
The level of pain felt was assessed using the VAS scale and significantly changed in the months following the procedure, with the highest values being noted before the operation, while the lowest were noted a year after the procedure. There were no statistically significant differences between men and women. The average assessment of pain at the moment the study started was 6 on a scale from 1 to 10. This assessment was taken into account later as a point of reference for the division of results using the VAS scale. The number of obtained points on the ODI scale was considered to indicate a downward trend, even in the case of patients with the highest degree of radiological advancement of degenerative changes (degree 5), according to the Pfirrmann scale. Furthermore, the results of the SWLS questionnaire reveal a significant increase in satisfaction with life in the subsequent stages of the study. Bearing in mind specific stages of the study, significant differences in the assessment of pain, disability, and satisfaction were observed in specific groups based on the Pfirrmann scale ( Table 2).

Correlation of VAS, ODI and SWLS scale assessments.
The conducted correlation analysis revealed significant dependencies in the assessment of quality of life in regard to pain and degree of disability (Table 3). A higher level of satisfaction was correlated with a lower level of pain as well as a higher level of fitness.
The level of pain and the degree of disability were closely related to the degree of radiological advancement of degenerative changes according to the Pfirrmann scale (Table 4). Improvement in quality of life was observed significantly more often among people with a lower degree of advancement of the disease.
Among all the respondents, the percentage of patients in whom there was an improvement in quality of life increased in the months following the operation in the group of people who classified their pain below 6 on the VAS scale (Fig. 1).
In the months following the surgery, alongside an improvement in the quality of life, increasing participation from patients with higher fitness was also visible (Fig. 2). The initial data revealed that the chance of satisfaction with life significantly decreased with a 1-point increase in the result of the SWLS questionnaire (OR 0.79; 95% CI 0.735-0.862). Similar results were observed after 3 months-OR 0.83; 95% CI 0.778-0.892, 6 months-OR 0.86; 95% CI 0.809-0.921, and 12 months-OR 0.91; 95% CI 0.860-0.964.

Discussion
There have been numerous RCTs and systematic reviews conducted with the same research purposes and even larger numbers of patients; however, the vast majority of these studies have concentrated on assessing quality of life, IVD degeneration, and patient disability before surgery and at specific postoperative periods, without considering the degree of radiological advancement of degenerative changes, according to the Pfirrmann scale, as a criterion.      Using the generally accepted exclusion criteria, the number of articles in English totaled 202, of which there were 189 full-text articles available, and when the criterion of human studies was applied, 143 articles were initially qualified. Next, we (Rafał Staszkiewicz and Beniamin Oskar Grabarek) independently analyzed these 143 articles, finding that only 5 were directly related to our study objective [18][19][20][21][22] . It is also notable that none of these articles involved the Polish population. We followed the same procedure when searching the database using the words "disability" AND "Pfirrmann scale" OR "radiological advancement of degenerative changes", which allowed us to initially indicate 287 articles, of which 256 were in English, 242 were available as full-text articles and 190 regarded humans. However, this time, none of these articles touched on the target topic. www.nature.com/scientificreports/ Therefore, we believe that the analysis we conducted is very significant and constitutes an important supplementary study in terms of quality of life and disability (Health Science) among patients with degeneration of the L/S spine section.
In our study, we assessed quality of life among patients whose degree of radiological advancement of degenerative L/S spinal changes and pain led to qualification for neurosurgical microdiscectomy of the L/S spine.
The first part of the analysis we conducted confirmed that an increase in the advancement of IVD degenerative changes in the L/S spine section was accompanied by a statistically significant increase in the frequency of taking www.nature.com/scientificreports/ NSAIDs. Significantly, almost all patients (81.8%) with degree 5 degenerative changes took pain medication every day. This indicates that the patients' daily lives were marked by considerable pain and suffering. However, we did not find that habitual consumption, such as alcohol consumption or cigarette smoking, has an influence on the occurrence of IVD degeneration of the L/S segment. This is in line with the observations of Zhang et al., who critically reviewed the literature and reported that moderate alcohol consumption is a factor preventing IVD degeneration 23 . In turn, smoking cigarettes is an unfavorable prognostic factor for IVD degeneration, as confirmed by Chen et al. 24 .
We then assessed pain intensity, quality of life, and degree of disability among patients, both before the neurosurgical procedure and in the 12-month period following it. First, we noted that the greater the degree of IVD degeneration, the more patients reported pain of a higher intensity. It should be noted that patients with degree 5 degenerative changes declared maximum pain intensity (10 points), which decreased by only 2 points 12 months after the operation.
In most patients, pain was a daily occurrence. This pain was of moderate or strong intensity in nature. These studies confirmed that unfortunately, pain is an inherent element of degenerative spine disease and affects the lives of both patients and their families 25 . Research by Chin et al. among patients with atypical changes and low back pain confirmed a statistically significant improvement in terms of pain and level of disability after microdiscectomy. Patients, both with and without steatosis and edema of the spinal bone marrow, showed a significant improvement in the postoperative VAS score for low back pain 26 .
Our results correspond with the data of other authors who studied pain intensity in relation to IVD disease using the VAS scale. It should be noted that both the observation period and data collection vary, which makes comparing results more difficult. Puolakka et al. analyzed risk factors for absence from work caused by L/S spine section pain in patients after surgery. The observation period in these patients was 5 years after surgery, while 2 months after the operation, data on pain intensity were collected based on the VAS scale. A significant reduction in pain following the procedure was reported 27 .
In turn, Solberg et al. conducted a study that aimed to assess pain intensity among patients with IVD degeneration of the L/S spine section before a neurosurgical procedure and 12 months after. In the case of pain in the L/S spine region, the pain intensity decreased from 5.17 to 2.13 (p < 0.001), whereas in the case of appendage pain, it decreased from 6.34 to 1.68 (p < 0.001). In both assessments, the reduction in pain was significant and noticeable 28 . It follows that regardless of the observation period, the surgical procedures performed due to IVD degeneration of the L/S section result in a noticeable reduction in pain.
Furthermore, using a dedicated ODI questionnaire for the assessment of the degree of disability caused by degenerative changes in the L/S spine section, we determined that overall, microdiscectomy resulted in a decrease in disability, assessed at the beginning from 18 points (moderate disability) to 12 points (minimal disability). None of the patients declared full disability; however, the more intense the radiological changes were, the lower the fitness of the patients was.
The observations described by Middendrop et al. confirmed that the degree of radiological advancement of IVD degenerative changes of the L/S spine section positively correlates with decreased fitness in patients. These authors found that the ODI results of the patients fluctuated, ranging from 0 to 91.11% (arithmetic mean 32.77% ± 17.02%). The largest group of patients (48.39%) had moderate functional disability (ODI result between 21 and 40%) 29 .
Additionally, Hasanović-Vučković et al. assessed the fitness of 100 patients with degenerative disease of the L/S segment, noting a distribution close to ours for the number of patients at individual degrees of radiological advancement of degenerative changes, according to the Pfirrmann scale (1-0.75%, 2-14.25%, 3-37.5%, 4-36.5%, and 5-11%) 22 . In our study, the largest number of patients had degree 3 (38.1%) and degree 4 (28.3%) IVD degenerative changes.
These authors reported a statistically significant correlation between the degree of advancement of changes and VAS (r = 0.16) and ODI (r = 0.24) scores 22  Nonetheless, Grasso et al. confirmed effectiveness, reduction in pain, and improvement in quality of life among patients in whom hybrid surgery was conducted due to radiculopathy or cervical myelopathy 21 .
We also indicated that the best results for the surgery were achieved at the lowest degrees of advancement of degenerative changes. Furthermore, we confirmed a strong correlation between the level of pain, disability, and quality of life. A higher level of satisfaction was correlated with a lower level of pain as well as a higher level of fitness. Improvement in the quality of life was significantly more often observed among people with a lower degree of disease advancement, although larger differences in quality of life between the subsequent observation months were noted for higher degrees of disease advancement. The percentage of patients with improved quality of life increased in the months following the operation in the group who classified their pain below 6 on the VAS scale. It follows that pain plays a large role in how well-being is perceived by patients, and its reduction or elimination is a particularly important issue. www.nature.com/scientificreports/ In the case of the initial data, the chance of being satisfied with life significantly decreased with a 1-point increase in the result for the SWLS questionnaire.
Kurowska et al. proved that people who have diseases of the lower segment of the spine and have developed depression experience chronic pain of a much greater intensity 31 .
Other authors also noted a significant improvement in the quality of life and life satisfaction after surgery due to IVD degeneration of the L/S spine section-sectional area, cross-sectional area difference index (CDI) and fat infiltration rate (FIR) of the multifidus, erector spinae and psoas major at the apical vertebral level were measured using MRI. The visual analogue scale (VAS) score, Oswestry Disability Index (ODI) and 36-item Short Form Health Survey (SF-36) score were used to evaluate patient quality of life. Correlations between the degree of asymmetric muscular degeneration and quality of life were analysed. The CDI of the multifidus, erector spinal and psoas major was higher in the DLS group compared with that in the control group. The CDI of the multifidus was found to be positively associated with the Cobb angle of lumbar scoliosis. Similar results were obtained for fat infiltration between the two groups. In addition, the CDI and FIR difference index of the multifidus was positively correlated with the VAS score and ODI but negatively correlated with the SF-36 score. The quality of life significantly decreased with increasing asymmetric atrophy and fat infiltration in the multifidus. Thus, strategies to enhance the function of the multifidus may have a positive impact on quality of life 32,33 . Of course, it should be remembered that the microdiscectomy procedure alone did not have an influence on the improvement in quality of life; it is likely that the rehabilitative treatment after surgery, coordinated by a rehabilitation specialist, also played a role.
Our study has both strengths and weaknesses. A strength of this study is that the analysis was conducted on a relatively large number of respondents who underwent microdiscectomy in one clinical center, considering that different surgical methods are also used for treating IVD degeneration of the L/S segment. Additionally, pain intensity, degree of fitness, satisfaction with life, and the success of neurosurgical treatment based on the degree of advancement of degenerative changes in the IVD of the L/S spine section according to the Pfirrmann scale were also evaluated. In the available literature, there are few observations on the quality of life among patients with IVD degeneration of the L/S spine section depending on the degree of radiological advancement of lesions [18][19][20][21][22] . The first limitation of our study is the observation period of 12 months after microdiscectomy. Of course, it would be very interesting and cognitively important to assess the quality of life in this group of patients over a period longer than 1 year. The second limitation is the fact that this was a single-center study, in which the number of patients representing the individual degrees of IVD degeneration was not uniform. Although the total number of patients may seem small, our statistical analysis indicated that 113 cases constituted a sufficiently representative group, allowing for analysis to be conducted and a reliable result to be obtained. Furthermore, pain and its influence on everyday functioning is a subjective feeling that is dependent on many factors. Its perception is influenced by emotional, pathological, genetic, and other cognitive elements. Of course, the obtained results might also have been influenced by the fact that we used only one questionnaire that is commonly employed to assess quality of life. However, using a questionnaire consisting of a larger number of questions, such as the SF-36, would allow us to assess quality of life with consideration of other criteria. Nevertheless, when comparing the strengths and weaknesses, conducting our study can be determined as justified, as it contains valuable research findings. It is a milestone study in research regarding quality of life and disability in patients following a microdiscectomy procedure due to IVD degeneration of the L/S spine. In summary, the pain level, which was assessed using the VAS scale, significantly changed in the months following the surgery, with the highest values noted before the surgery and the lowest a year after the operation. The results of the SWLS questionnaire revealed a significant increase in satisfaction with life in the subsequent stages of the study. When considering individual stages of the study, significant differences in the assessment of pain, disability, and satisfaction were observed in individual groups based on the Pfirrmann grading scale. MRI is a significant component in the diagnosis of degenerative disease, while microdiscectomy is an effective surgical method for the treatment of degenerative changes in the IVDs of the L/S spine. Furthermore, our analysis indicated that the highest chance of returning to fitness, at a level equal to or close to the level prior to the occurrence of IVD degeneration, after the microdiscectomy procedure occurs in patients at early degrees of radiological advancement, such as 2 and 3. Therefore, patients should not delay the decision to undergo surgery when there are clinical grounds for it. The role of the neurosurgeon is to explain to the patient in detail the essence of the disease, possible treatments, advantages, and possible side effects of surgery. Therefore, the physician must partner with the patient and exhibit highly developed communication skills.

Materials and methods
Participants. In this study, 113 Caucasian patients, consisting of 55 women (48.7%) and 58 men (51.3%) who were qualified for surgical treatment of intervertebral disc degeneration of the lumbosacral spine (microdiscectomy) were enrolled. The surgeries were carried out in the period from March 2020 to April 2021, always by the same team of neurosurgeons, under the leadership of Rafał Staszkiewicz. The observation period ended in May 2022. All patients were treated and underwent surgery in the same clinic, Department of Neurosurgery, 5th Military Clinical Hospital with the SP ZOZ Polyclinic in Krakow, 30-901 Krakow, Poland. The inclusion and exclusion criteria were the same as in our previous paper 34 and are presented in Table 5.
Each patient underwent a neurological examination including an assessment of muscle strength; passive movement; muscle tension; patellar, ankle, plantar, Babinski sign, and Rossolimo sign reflexes; surface and deep sensation; gait; mobility; and L/S spine pain. The study excluded cases of patients who presented with loss symptoms, as such patients required emergency neurosurgical intervention; we undertook evaluation only among stable cases ( www.nature.com/scientificreports/ In all patients, before the microdiscectomy procedure, a magnetic resonance imaging examination was conducted (Signa Hde 1.5 T General Electric Medical System, Poland) using the projections SE T1, SE T1 FLuid-Attenuated Inversion Recovery (FLAIR), FSE T2 and Short Tau Inversion Recovery (STIR) sequences in transverse and sagittal sections in 3 mm and 4 mm thick layers. This allowed for the determination of the degree of radiological advancement of degenerative changes, according to the Pfirrmann scale from 1 to 5 (Fig. 3). The analysis of the MRI images, including the determination of the degree of IVD degeneration according to the Pfirrmann scale, was performed independently by two neurosurgeons (Rafal Staszkiewicz, MD, PhD, and Dorian Gładysz, MD) employed at the Department of Neurosurgery, 5th Military Clinical Hospital with the SP ZOZ Polyclinic in Krakow, 30-901 Krakow, Poland. In a situation where the abovementioned specialists determined a different degree of lesions, the Department Head-Wiesław Strohm, MD, PhD-had the decisive opinion. Out of 113 cases, only in three cases (2.65%) did the assessment of the degree of IVD degenerative changes differ.
In 27 (23.9%) patients, radiological changes were classified as grade 2 degeneration; in 43 (38.1%) patients, they were classified as grade 3; in 32 (28.3%) patients, they were classified as grade 4; and 11 (9.7%) patients were classified as having grade 5 advancement of changes on the Pfirrmann scale. Furthermore, qualification for surgery consisted of conducting a neurological examination as well as conducting physical and subjective examinations in each patient.
After being discharged from the Department of Neurosurgery, patients were required to report themselves to the Neurosurgery Clinic within 4 weeks of the procedure for routine inspection. Subsequently, patients were recommended rehabilitation and were informed about subsequent proceedings.
Patients were asked to complete all questionnaires before surgery (month 0) as well as 3, 6 and 12 months after it was carried out. www.nature.com/scientificreports/ Microdiscectomy procedure. In each patient, the microdiscectomy procedure was performed under general anesthesia in the abdominal position. A 2-4 cm skin incision was made over the affected interbody space, identified intraoperatively by fluoroscopic X-ray. Once the right space was identified and the skin incision was made, the posterior surface of the vertebral arches was exposed with the help of special surgical instrumentation, holding the previously separated spinal muscles. This was followed by an incision of the yellow ligament, which was lifted in a small space, opening the lumen of the spinal canal. After assessing the intracanal conditions and exposing the hernia, the IVD and IVD sequestrator were removed. After the procedure was completed, a drain was placed at the wound site to drain accumulated blood, which was then removed after 24 h. Patients were verticalized on the first postoperative day, and early rehabilitation in the Neurosurgery Department was included. The patient's length of stay, including preoperative diagnosis, anesthesia consultation and early postoperative period, was 5 days.
The satisfaction with life scale. The respondents answered 5 questions, which were measured using a 7-point scale, wherein 1 on the scale signified "definitely disagree" with the statement, while 7 signified "definitely agree" with the statement. The test has high internal consistency and test-retest correlations. In our study, the SWLS questionnaire on quality of life was assessed for 3 possible situations: Statistical analysis. Analysis of the data was conducted using the procedures of the Statistica 13.3 (Stat-Soft, Poland) program. Categorical variables were presented using numbers and percentages of cases in each group. The χ 2 independence and Fisher tests were used. Numeric data were presented as the mean with a standard deviation (X ± SD) in the case of a normal distribution; otherwise, they were presented as a median with quartiles-M (Q1-Q3). Compliance with a normal distribution was verified using the Shapiro-Wilk test. The significance of differences in groups was checked using the Mann-Whitney U test, the Kruskal-Wallis test and the Friedman test for repeatable measurements. Correlation analysis was conducted using Spearman's correlation coefficient with a significance test. Additionally, odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated based on univariate logistic regression models. A p value below 0.05 was considered statistically significant.   40 . For this population, the maximum error value was estimated at 9%. Therefore, assuming a p value < 0.05, the required number of respondents in the study was 119 (p value < 0.05). In turn, according to data obtained from the European Health Survey in 2019, 25.8% of adult Poles above 18 years old (n = 31,435,677) suffered from pain in the L/S section of the spine 41 . For this population, the maximum error value was estimated at 9%, and the required number of participants in the study was 100 (p value < 0.05).